The present invention relates to filtration. More particularly, the invention relates to a filtration system or quality control of cooking fats and cooking oils.
In the culinary industry filtration is generally employed to purify used cooking fats and cooking oils. In the absence of such purification, impurities build up in the fats and oils to a level which is unacceptable by industry standards.
As fats and oils are used in cooking, they tend to break down, degrade, and hydrolyze to free fatty acids, glycerol, and other polar products. The free fatty acids are among the more harmful products of this degradation. The recommended maximum acceptable level for free fatty acids is three to four percent.
The prior art discloses filtration systems for removing such impurities from cooking fats and cooking oils; see, e.g., U.S. Pat. Nos. 5,597,601, 4,747,944, 3,667,613, 5,247,876, 3,107,601, 2,698,092, and 3,630,361. What is lacking, however, is a filtration system which is adjustable in accordance with the quality of the cooking fat or cooking oil which is being filtered. The present invention provides such a system.
More specifically, the prior art fails to provide filtration apparatus in which a predetermined portion of the cooking fat or cooking oil is recycled or routed to the filtration system before being discharged therefrom. For example, U.S. Pat. No. 4,747,944 to George discloses a filtration system in which filtrate is recirculated by being discharged into a vessel which contains unfiltered cooking fat or cooking oil. The mixture of partially-filtered fat or oil is then returned to the filter. An obvious drawback of this system is the absence of any mechanism for controlling the proportion of the fat or oil which is recycled to the filter. A second apparent limitation is the requirement of a vessel for mixing the liquid discharged from the filter with untiltered liquid.
British Patent 751,892 discloses a filtration system for mineral oil. The system includes a part-flow filter cartridge which controls the proportion of mineral oil which is recycled to a filter. It will be apparent to those skilled in the art that this control mechanism lacks flexibility with regard to varying the proportion of fluid which is routed or recycled to the filter. This limitation is particularly serious with regard to the desirability of continuous variation of the proportion of fluid which is recycled, or which is routed to the filter before being discharged from the filtration system.